Question

2(a). Find the equation of the line which passes through the points A(−2,7) and B(2,−3).
(b) Given that (5b−a)/(8b+3a) = 1/5, find, correct to two decimal places, the value of a/b.

Accepted Answer

(a) Gradient m = (y₂−y₁)/(x₂−x₁) = (−3−7)/(2−(−2)) = −10/4 = −5/2. Equation: y−(−3) = (−5/2)(x−2) ⇒ 2(y+3) = −5(x−2) ⇒ 2y+6=−5x+10 ⇒ 2y+5x−4=0, i.e. 2y+5x−4=0.

(b) (5b−a)/(8b+3a) = 1/5 ⇒ cross-multiplying: 5(5b−a) = 8b+3a ⇒ 25b−5a=8b+3a ⇒ 25b−8b=3a+5a ⇒ 17b=8a ⇒ a/b = 17/8 = 2.125 ≈ 2.13 (2 d.p.)

WAEC Mathematics 2019 Theory — Question 3

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